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91.
The photothermal degradation of copolymers of methyl methacrylate (MMA) and n-butyl acrylate (n-BuA) covering the whole composition range has been studied at 165°.The gaseous products, which are relatively minor, are hydrogen, carbon monoxide and methane. The liquid products are predominantly MMA, with n-BuA, n-butanol and n-butyraldehyde as minor products. Infra-red spectral changes in the residue were attributed to lactone formation and associated with butanol formation as in the purely thermal reaction The “cold ring” or chain fragment fraction becomes increasingly more abundant as the n-BuA content of the copolymer is increased.All the products and principal features of the reaction are explained in terms of a radical process which is initiated by scission of pendant acrylate units and is propagated by a combination of depropagation and intra- and intermolecular transfer processes, the relative importance of which depends upon copolymer composition. Differences from the thermal reaction and the corresponding reaction in copolymers of methyl methacrylate and methyl acrylate are discussed.  相似文献   
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Summary We introduce a new three-stage process for calculating the zeros of a polynomial with complex coefficients. The algorithm is similar in spirit to the two stage algorithms studied by Traub in a series of papers. We prove that the mathematical algorithm always converges and show that the rate of convergence of the third stage is faster than second order. To obtain additional insight we recast the problem and algorithm into matrix form. The third stage is inverse iteration with the companion matrix, followed by generalized Rayleigh iteration.This work was supported in part by the National Science Foundation and the Office of Naval Research.  相似文献   
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The opportunity to test a new equation for the computation of the lattice energy and at the same time examine a disparity in the literature data for the enthalpy of formation of the azide ion, ΔHθ?(N3?) (g) was the motivation for this study. The results confirm our earlier calculation and show the new equation to be reliable. Thermodynamic data produced in the study take values: ΔHθ?(N3?)(g) = 144kJ mor?1ΔHθhyd(N3?) = ?315 KJ mol?1 or ΔHθhyd(N3?) = ?295 KJ mol?1UPOT(NaN3) = 732 kJ mol?1UPOT(KN3) = 659 kJ mol?1UPOT(RbN3) = 637 kJ mol?1UPOT(CsN3) = 612 kJ mol?1UPOT(TIN3) = 689 kJ mol?1. The lattice energies of azides whose enthalpies of formation are documented have been calculated as well as the enthalpy of formation of the azide radical.  相似文献   
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From the linearized, time-independent, constant depth, shallow water tidal equations in an f-plane for a two-layer estuary, two independent modal Helmholtz equations are derived. These modal equations are solved using a fifth-degree finite element technique. The first and second space derivatives of the complex modal tidal elevations, and thus the modal currents and their first derivatives, are evaluated directly from the solution at each node of the finite element mesh. The Stokes drift, which is the major part of the residual tidal flow, is evaluated from these nodal values of the currents and their derivatives. Good agreement is obtained with the exact analytical solution for a wedge-shaped estuary with a wedge angle of π/3, using a mesh of 64 equilateral triangles with sides approximately 1/10 of the wavelength 2πC2/σ of a Kelvin wave solution for the short-wavelength mode.  相似文献   
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